An organic electroluminescence device (OLED) is a self-luminous display device and requires no backlight, and thus has an advantage capable of being lightweight and thin.
However, there is a disadvantage that the OLED panel causes reflection due to external light by metal wiring or electrodes to greatly reduce a contrast ratio.
Patent Document 1 (Japanese Unexamined Patent Publication No. 2014-186351) discloses a technique of attaching a circular polarizing plate to an OLED panel in order to prevent a decrease in the contrast ratio due to reflection of external light. According to Patent Document 1, external light incident from the outside enters through the circular polarizing plate, and the incident external light is reflected by the second electrode made of metal to change its polarization direction. Therefore, the incident external light does not transmit through the circular polarizing plate and does not emit to the outside, thereby causing extinction interference. As a result, by blocking external light to be reflected, the contrast ratio is improved.
However, when the circular polarizing plate is used, there is a problem that the luminance of the display is greatly reduced to 50% or less. In addition, as the display device gradually evolves into a bendable or foldable flexible display device, there is a limitation to use a circular polarizing plate by attaching it to an OLED panel, for a reason of deterioration in the performance appearing in areas where the curvature of the circular polarizing plate is large due to bending and folding.